Magnetic centering device for cathode ray tubes



1951 D. P. INGLE ET AL 2,574,039

MAGNETIC CENTERING DEVICE FOR CATHODE RAY TUBES Filed March 17, 1951 fmlenz orr Patented Nov. 6, 1951 UNITED "s'irATE AT NT QFFWE MAGNETIC CENTERING DEVICE" FOR Q H BE 7 Donald Paul Ingle, Defiance, and so! L. Realms,"

I Cleveland, Ohio, assignors to All Star-Products, ..-Inc., Defiance, Ohio, 'a corporation of Ohio Application February 17, msgserial No; 21i,4ss f available screen area'imost efficiently, itis desir able to center the beam relative to the screen. It-

is not possible in practical commercial equipment to construct the apparatus so that the beam is centered, since practical manufacture, particularly of the electron gun and associated-partsof the cathode ray tube, requires reasonable tolerance allowances.

For this reason it is essential in apparatus using cathode ray tubes to provide beam centering devices capable of shifting thebeam-within thetolerance range of the apparatus. 'Since the deviation of the beam' from the centered value may be in any amountwithinthe-tolerance limit and may bein any direction, itis necessary that the centering apparatus be adjustable as to direction and amount of the centering shift imparted to the ray beam.

In accordance with the present invention an improved device is'provided to accomplish this centerin adjustment of the ray beam. Briefly,

a pair of soft iron straps straddle the neck of the neck of the tube oriented transversely of theray beam and having adjustable polarity and intensity. I I 1 In a modified formof the present invention, three straps encircle the neck'of the cathode ray tube, the straps each extending partially about the neck of the tube and forming three nonmagnetic gaps. The straps in the region of two of the gaps extend radially outwardly as described above to receive two-movable permanent magnets. The resultant'magnetic field within the neck of the tube can-be adjusted inorientation, polarity, and intensity by-suitable movei ment of the'magnets;

9 Claims: (01. 313 76) '5 5,-Figure 4 I 7 V Figure6 is a cross-sectional view like Figures It is therefore a general object of the present invention to provide an'improved centering device for the ray beam of a cathode ray tube and providing a magnetic field of adjustable polarity and intensity.

Another object of the present invention is to provide an improved centering device for the ray beam 'of a cathode ray tube that is of smallsize and 'light weight and capableof being received upon and Supported by the neck of the cathode ray tube. v I

7 Still another object of the present invention is to provide an improved centering device for a cathode ray'tube'that'utilizes permanent magnets as a field producing means.

It isyet another object of the present invention" to provide 7 a very simple, compact and light Weight centering means for a cathode ray tube beam which utilizes permanent magnets and. produces a magnetic field of adjustable orienta tion; intensity, and direction.

Further it is an object of the present invention to provide an improved centering device for a cathode ray'tube that is simple, inexpensive, requires no mounting elements, and is adjustable by a shaft extending. backwardly of the cathode ray tube whichcanrbe made readily accessible from the rear of the television receiver or similar device and is electrically unconnected with any vention itself,however, both as to its organiza-' tion and method of operation, together with further objects andadvantages thereof, will best be understood by, reference to the following description taken in connection with the accompanying drawings, in which:

Figure 11 is a view in perspective showing a centering device of the present invention mounted on the neck of aicathode ray tube, the device being shown in somewhat enlarged proportion in relation to the .cathode'ray tube;

Figure 2 is a side elevational view with parts in cross-section showing one form of the presentinventionin enlarged scale;

Figure3 is a cross-sectional view through axis 33-,'Figure-,2; V i 7,

Figure 4 is a view'like Figure Z showing an alternative embodiment of the present inventibn; 3

Figure 5 across-sectional view through axis beam producing means or electron gun located adjacent the base B, these electrodes being indicated generally at E. r

The electrodes E comprise a tubular cathode l0 having its end Illa closed as shown-in Figures 2 and 3. A heater unit (not shown) is positioned inside the cathode and operates, when energized, to heat the same to. electron emitting temperature. The conducting sleeve 12 encircles thecathode and has an inturned portion lZa defining a circular and window through which electrons emitted from the cathode. pass. This electrode forms a controlgridto vary the intensity of the cathoderay beam as desired to produce the desired image on the screen S. A second sleeve I4 is mounted adacent to and coaxially with the grid sleeve l2 and receives a positive potential in relation to the potential of grid sleevelZ This sleeve, whichacts as an electron accelerating device, has a pair of spaced inwardly extending centrally apertured disks Ma which act to limit the ray beam and partially focus the same. Thelast ray producing electrode is the focussing sleeve [6 which is coaxial with and slightly larger than the accelerating electrode, Sleeve IB is positioned'adjacent.theend of the electrode 14 so as to. define a double sleeve electron lens in conjunction therewith. The potential applied to this electrode isadjusted in relation to the potential of, the accelerating electrode so as to focus the raybeam at a point on the surface of the screen. S to. produce, a sharp spot thereon. c 1

The foregoing elements produce a ray beam generally directed in an axial direction in relation to the tube T to impinge upon the screen S. However, in practical commercial tubes, it is not possible to secureprecise alignment and there is a certain amount of inevitable; deviation from this condition. It is the purpose of. the mechanism of the present invention'to correctfor thisdeviation .in a highly effective and yet inexpensive and convenient manner- -In the form of the present, invention shown in Figures 1 to 3, a pair of soft-iron straps l8 and of shape to conform to the shape of the. neck.

of the tube and in the form of two halves extend about the neck of the tube. These'straps extend radially outwardly at their ends in ears forming two sets or pairs of plane facesjas indicated at l8a, l=8b, 20a, and 20b, The faces 18a and 20a are apertured and receive the screw 22 and nut 24 which can be tightened or loosened to grip the neck N as desired.

At portions I81) and 20b, the straps I8 and 20 form a cavity. The yoke 26 of brass, plastic, or similar non-magnetic material, is sandwiched between these portions of' the straps. as shown to form a non-magnetic spacen. The portions 18b and 201) are secured to this spacer-by. the. rivets 21, thus forming a rigid cage.

The web portions 260 of theyoke '26 has a bore 26d disposed coaxially with the cage formed by the parts I81) andZOb. bere, forms a bearing which receives the shaft 28 which extends into the space between portions.|8b; =and- 'ZQbpf the y m the. desired motion across the screen straps l8 and 20 in an enlarged portion 28a. A permanent magnet 30, described hereafter, is positioned on the end of this shaft as shown. An outrigger shaft 32 has an end bore 32a which is received over the protruding end of the shaft 28 and is rigidly secured thereto by the set screw 34 which is threadedly received by the shaft 32. The outrigger shaft 32 may be of insulating material if the unit is not grounded and of conducting material if the unit is grounded.

The magnet 30 is of any eflicient permanent magnet material such as, for example, Alnico, which is an alloy of aluminum, nickel, and cobalt. This. magnet isof such cross-section that it can be, made to produce. opposed faces magnetized in opposite polarity: In a cross-section such as shown in Figure 3, face 30a. is of one polarity, say north, and face 301) is of opposite polarity, say south; Thus, when faces 30a and 301) are aligned with portions l8b and 20b of the straps l8 and 20, espect v ly str in" is a; n rt P and strap 20 a south pole and the space between the straps (and hence the interior of the neck N) 'has a corresponding magnetic field, Similarly, when the shaft 32 is rotated from this position to locate face 3 017. adjacent portion 39b of the strap 28 and the face. 30b adjacent portion 18a of strap [-8, the latter strap is a south pole and strap 20 is a north pole, thus giving. rise to a magnetic fi d f pposite pola ity,

When the shaft 32 is adjusted-to orient the faces 30a and 30b. to an intermediate position as o n in'F sure the magnet-fi i less ef c iv in, producing a magnetic field; within the. confines of the neck N of; the tube because theleakage flux between the magnet poles is greater, When the faces 33a, and 30b are vertically oneabove the other, the field is of zero intensity within the neck N. Thus roba 2ipn of the magnetqfifl, varies the polarity and the intensity of the; magnetic field within the neck N of the tube; 7,

The ray beam from the electron gun E travels at high velocity in the direction of the arrow 36, F ure 2- S nce h ma netic field between the straps l8 and20 is oriented transversely to this direction of travel, the beam is deflected up or down as shown by the arrow 38., Figure 3, the amount and direction 'of this deflection being pe to po ition. of the. shaft C sequently, the shaft may be rotated until the ray beam strikes the desiredcenter point of -the cathode ray tube screen S, thus. compensating for eccentricities in the tube.

The magnetic sweep. device 40, Figure 1, produces a magnetic field: as. required to direct the S. In television service, for. example, this motion is. a r pe it ve s rai ht line. scanning y le- I this portion of the unit introduces any eccentricity or shift of the ray. beam when in the energized condition, thegbeamcan be restored to the centered cflndition by appropriate rotation of theshaft 32. In'othsr wordsgthe'shaft 32 can be rotated to compensate not only for tolerances in the cathode ray tube itself but also in the deflecting devices or the electric circuits energizing them and various stray fields-such asthe earths field.

The unit shown. .in Figures 1 to 3 is capable of Sh t g the ray. beam inone direction in the o nt quired to center the. beam. An additional unit may be used ir desired to center the beamin th opposite, direction. this being offset approximate y .90? in relationto the first unit. erna ivelmthestraps;l8 and 3.0 may be held on the neck N of the tube T rather.- loosely and the unit rotated until the direction of the field between the straps is transverse to the eccentricity of the ray beam. The beam may then be centered by appropriate rotation of the shaft 32.

Figures 4 and 5 show an alternative embodiment of the structure of the present invention.

In this figure parts corresponding to those of.

Figures 1 to 3 are identified with the number I added to the identifying numeral. The structure of Figures 4 and 5 differs from that of Figures 1 to 3 in that the ears H81) and I20b extend out from neck N so as to define a channel I I9 in conjunction with the portions of I26! and I26b of yoke I26.

The web I260 of the yoke I26d is of such crosse section so as to prevent rotation of the magnet assembly. The rod I28 is slidably received in this opening and carries at itsend a bar magnet I30 of cross-section as is described on page '7, lines II, I2, I3. An outrigger shaft I32. has an opening which receives the end of shaft I28 and is secured thereto by the set screw I34 as shown so that the shaft I32 may be shifted forwardly or backwardly to alter the position of the magnet I30 in relation to the straps H8 and I20. This outrigger shaft may be of insulating material if the unit is not grounded and of conducting material if the unit is grounded.

The magnet I30 is of Alnico V (an aluminum, nickel, cobalt alloy) or similar efficient permanent magnet material. One end, say end I30a, is magnetized to form a north pole on face I300 and a south pole on face I30d. The other end, I301), is oppositely magnetized to form a south pole on face I30c and a north pole on face I30d. When the shaft IE2 is shifted, to cause ends I30a and I30b to move in relation to the straps I I8 and I20, the straps are magnetized in accord with the portion of the magnet I30 in registry with the ears H81) and I202). The polarity of the field is in one direction (strap I I6 north, strap II 8 south) with end I30a between ears I I81) and I20b and the opposite direction with the end I30b between the ears. At intermediate positions the intensity of the field is less than at the extreme positions but the polarity is in accord with the end of the magnet nearest the straps H6 and H8.

The unit of Figures 4 and 5 operates to deflect the ray beam up or down as shown by thearrow I38. If it is desired to deflect the beam in two directions, a second unit, transverse to the first and offset lengthwise along neck N may be employed.

Figure 6 shows another embodiment of the present invention capable of shifting the ray beam in any direction on the screen S, Figure 1. This unit includes three soft iron straps 2 I8, 2I9, and 220, each extending partially about the neck N of the tube and each having ears extending radially outwardly as shown at 2I8a, 2I8b, 2I9a, 2I9b, 220a, and 2201). The ears 2I8a. and 2201) receive the screw 222 and nut 224 to secure the unit to the neck of the tube by adjustable compression.

The ears ZIBb and 2I9a and the ears 2I9b and 220a are like the ears I81) and 201), Figure 3, to form a cavity. The cars are held in position by the non-magnetic yokes 226 which are like the yoke 26, Figure l. Magnets 230 are rotatably mounted within each cage so defined in the same manner as the magnet 30, Figures 2 and 3, these magnets being magnetized like magnet 30 so that their opposite faces have opposite polarities.

.The operation of the of Figure can be visualized by considering the operation'of the magnets 230 separately. The magnet within the cage formed by the ears 2I8b and 2I9a acts to magnetize straps 2I8 and 2I9 to produce a field in the center of the tube extending generally in the direction of arrow 200, thus providing control of the position of the ray beam in the direction transverse to this arrow. Similarly the magnet within the cage formed by the ears 2I9b and 220m acts to magnetize straps 220 and 2I9 to'produce a field at the center of the tube extending generally in the direction of arrow 202, thus providing control of the position of the ray beam in the direction transverse to this arrow. Together, the magnets control the position of the ray beam in both directions and thereby control the centering of the ray beam in each direction on the screen S.

It will be noted that the magnet I30 is approximately twice the width of the straps H8 and I20 so that one half or the other of this magnet can be centered within the confines of the space formed by the ears H81) and I201).

If desired, a cushion such as a plastic sleeve encircling the straps may be interposed between the straps of the centering device and the neck N of the tube, thus permitting control of the grip of the straps on the tube without undue risk of tube breakage.

The term ferro-magnetic is used herein to designate materials, such as soft iron, having a high magnetic permeability in relation to air but no undue tendency for a residual magnetization. Theterm non-magnetic is used to designate materials such as plastics, brass, aluminum, and the like which have very low permeability in relation to ferro-magnetic materials.

While we have shown and described specific embodiments of our invention, it will of course be understood that numerous variations and alternative constructions may be made without departing from the true spirit and scope thereof. We therefore intend by the appended claims to cover all variations and alternative embodiments falling Within the true spirit and scope of the appended claims.

What we claim and desire to secure by Letters Patent of the United States is:

1. A magnetic centering device for a cathode ray tube having a neck containing electron beam producing means comprising in combination, a .pair of ferro-magnetic straps adapted to straddle the neck of the tube and, in position, defining a pair of circumferentially spaced gaps, the straps extending radially outwardly at one of the gaps to form a pair of ears with opposed faces, non-magnetic yoke means securing said faces in spaced relation to form a magnet-receiving space and forming a non-circular guideway extending parallel to the neck of the tube; and

- a rod snugly received in said guideWay for shifting movements parallel to the neck of the tube and carrying on its end and partially within the confines of said magnet-receiving space a permanent magnet of length approximately-twice the length of the space and having oppositely directed magnet poles at its ends cooperable reawaosa threev circumferentially spaced gaps, the straps.

extending radially outwardly at two of the gaps to form pairs of opposed ears, nonemagnetic means securing said. faces in. spaced relation to form a pair of magnet-receiving spaces, and

permanent magnets movably mounted. within.

said space to create. a magnetic field of'adjustable orientation, intensity. and directionv between the straps and transverse of the ray beam.

3. A magnetic centering device for a cathode ray tube having. a neck containing electronbeam. producing means comprising in combination, three ferric-magnetic straps adapted to encircle. the neck of. thetube andeach extending partially. about the same and, in position, defining three.

circumferentially spaced gaps, the straps extending radially outwardly at two ofthe gaps to form.

pairs of opposed ears, and permanent magnets.

tion, between the straps and transverse of the.-

ray beam.

4. A magnetic centering device for a cathode ray tube having a neck containing electron beam producing means comprising in combination, a pair of ferro-magneticstraps adapted to straddle the neck of the tuba-and in position, defining a pair of circumferentially spaced gaps, the straps extending radially outwardly at one of the gaps to form a pair of ears with opposed faces, nonmagnetic yoke means securing said faces in spaced relation to form a magnet-receiving space and forming a non-circular guideway extending parallel to the neck of the tube, and a permanent magnet slidably received in said guideway and having oppositely directed pairs of magnet poles spaced in the direction of sliding and selectively cooperable with the ears to magnetize the straps in controllable amount and polarity.

5. A magnetic centering device for a cathode tube having a neck containing electron beam producing means, said device comprising, in com.- binaticn, a pair of unitary compiementary'ferromagnetic straps spaced relative to each other to straddle the tube and, in position, defining a pair of circumferentially spaced gaps, one gap extending a substantial distance radially of the tube to form a magnet-receiving space, nonmagnetic yoke means sandwiched between the straps to sustain the same in fixed relative position at said one gap, and a permanent magnet having faces of opposite polarity disposed in said one gap and carried by the yoke means for rotations about an axis parallel to the tube for rotations to positions of adjustable registration with the ends of the straps defining said one gap, thereby to vary the intensity andpolarity of the magnetic field within the tube.

face thereof to define a pair of relatively. small.

diametrically opposed circumferential gaps, the. straps having ears extending a substantial dis-' tance radially outwardly in the region of one gap to form a magnet receiving space, non-magnetic means securing the straps together in fixed rela-., tive position at the opposite ends of the magn'etreceiving space, and a permanent magnet havingfacesof opposite polarity carried by said means in the magnet receiving space for rotations about anaxis" parallelto thetube axis tovary the intensity and direction of the magnetic field within thetube.

7. A magnetic. centering device for a cathode ray tube having a neck containing electron beam producing. means, the device comprising in combination, a pair of like unitary complementary ferroemagnetic straps adapted to straddle the neck of thetube and conform snugly to the surface thereof to. define a pair of relatively small diametrically opposed circumferential gaps, the strapsdefining radially. extending earsin the regions of said gaps, one pair of ears being of relatively small radial extent, adjustable non-mag-i neticsecuringv means extending between said one pair. of cars, theother pair of ears being of rela-.

tively great radial extent to form a magnet receiving. space, non-magnetic means securing the straps together at fixed spacing at said other pair of ears, and a. permanent magnet having faces of opposite polarity carried by said means in the magnet-receiving space for rotations about anaxis parallelto the tube axis to vary the in-.- tensity and direction of the magnetic field within thetube.

8. A. magnetic centering device for a cathode ray'v tube having a neck containing electron beam producing means, said device comprising, in combination; a pair of ferro-magnetic straps having complementary arcuate portions adapted to straddle the neck of the tube and substantially radial complementary portions contiguous therewith defining spaced ears, a non-magnetic yoke sandwiched between said ears to sustain them in fixed relative position, and a permanent magnet having faces of opposite polarity registrable with the ears respectively and movably carried by the yoke, the magnet being in spacedrelation with the ears at all times.

9. A magnetic centering. device for a cathode ray tube having a neck. containing electron beam producing means, said device comprising in combination; ferro-magnetic strap. means. defining complementary. arcuate. portions adapted to straddlethe neck of. thetube andsubstantially radial portions. contiguous therewith defining spaced ears, a permanentmagnet having faces of opposite. polarity cooperable with. the ears respectively to magnetize the arcuate portions of the strapmeans, and elements fixedly supported in;re lation tothe ears supporting the magnet for field. adjustingmotions with respect to, the ears and sustaining the ears in fixed relative position independent of magnet movement.

D. PAUL more. cm L. REICHES.

REFERENCES CITED The following references are of record in the file of this patent:

V UNITED STATES PATENTS Number 

